Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/12—Polysiloxanes containing silicon bound to hydrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/18—Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/42—Block-or graft-polymers containing polysiloxane sequences
  • C08G77/44—Block-or graft-polymers containing polysiloxane sequences containing only polysiloxane sequences
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/80—Siloxanes having aromatic substituents, e.g. phenyl side groups

Definitions

• the present invention relates to heat curable silicone rubber compositions. More particularly, the invention relates to heat curable silicone rubber compositions having improved clarity while maintaining desirable tear strength, oil resistance and compression set properties.
• Clear, heat curable silicone rubber compositions are known in the art.
• One such known composition comprises a mixture of one or more polymers, a high surface area filler of limited particle size and an index matching phenyl containing gum.
• Blends comprising polydiorganosiloxane gum having 5.3 mole percent phenyl substituents, and a silica filler have been reported to provide substantially clear rubber compounds exhibiting an 83.7 percent transmission, a yellowing index of 4.9, and a haze of 17.1 percent.
• phenyl based compositions are undesirable because they are costly to produce and may release harmful by-products over time.
• non- phenyl based materials are needed which not only have good physical properties but also have a high degree of clarity and low haze. Additional properties which are of importance in a clear silicone rubber composition are those which are associated with strength.
• tear strength, tensile strength, elongation, compression set and hardness are physical properties of interest. Tear strength, measured in pounds per inch (pi), is the ability of the material to withstand continual abrasion without breakdown in mechanical structure. Good tear strength is desirable because it is a measure of toughness. In addition to toughness, elastome ic aterials for most applications should have high tensile strength, measured in pounds per square inch (psi) .
• the tensile strength of a material is related to its ability to resist damaging tensile or pulling forces. At the same time, such materials require good elongation, which is the ability of the material to stretch without breaking. Elongation is measured as a percent of the original sample size. For some applications, hardness, measured on a shore A scale, is an important physical property. Other properties such as resiliency or the ability to recover shape after deformation, especially by compressive forces, may be desirable in a clear rubber product.
• U.S. Patent No. 4,539,357 discloses a heat curable silicone composition containing blends of high viscosity, vinyl terminated diorganopolysiloxane gums with a hydride-containing polysiloxane and peroxide curing agent. Although the composition may further comprise a vinyl containing organopolysiloxane resin copolymer of up to about 50 weight percent, Bobear '357 is primarily concerned with tear strength. Clarity of the resulting product is not evaluated among the properties of interest. Similarly, U.S. Patents Nos. 3,652,475 and 3,671,480 to ada et al. disclose heat curable elastomeric materials.
• U.S. Patent No. 4,061,609 to Bobear discloses a platinum catalyzed silicone rubber composition having a hydride resin component. In the examples, tear strength is evaluated but clarity is not.
• U.S. Patent No. 3,660,345 to Bobear shows a further example of an organopolysiloxane elastomer.
• U.S. Patent No. 4,891,393 to Hirai et al. discloses a thermal setting organopolysiloxane composition made from a gum with reinforcing silica and small percentages of methoxy groups, organohydrogenpolysiloxane and a curing catalyst.
• the materials exhibit improved adhesion to a variety of substrates including metals, glasses and plastics. Some examples listed in Table 4 appear to be transparent.
• U.S. Patent No. 4,746,699 to Modic discloses a curable silicone coating composition containing resinous organopolysiloxane components.
• the materials, which are compounded free of finely divided inorganic fillers, are reported as being transparent whereas compositions containing such fillers are translucent, or opaque depending upon the filler employed.
• U.S. Patent No. 4,041,101 to Jeram discloses a solvent resistant silicone rubber composition having a blend of vinyl containing polymers and resins, and a hydride containing resin or hydrogen containing polysiloxane cross-linking agent. A filler may also be present. Clarity does not appear to be discussed.
• SUMMARY OF THE INVENTION The present invention is based upon the discovery that a relatively small amount of an MQ resin acts as a compatibilizer between components predominantly containing D and Q units, respectively.
• a vinyl containing organopolysiloxane gum and a silica filler are combined with an MQ or MDQ resin or blends thereof to produce a clear silicone rubber which is heat curable in the presence of an organo-peroxide catalyst.
• the present invention provides clear, heat curable silicone rubber compositions having good strength properties.
• the compositions comprise, by weight:
• composition (B) about 1 to about 30 parts by weight of organopolysiloxane resin copolymers having MQ or MDQ units where each M unit can represent M or M' e.g., M- vinyl, units and where each D can represent D or D' e.g., D-vinyl units, and up to about 10 weight percent vinyl groups based upon Component (A) comprising:
• Component (D) in the form of an organic peroxide free radical initiator or curing agent is provided.
• composition may contain one or more of the following:
• (E) up to about 10 parts of a processing aid such as a low viscosity silanol stopped siloxane fluid of a about 3 to 500 centipoise at 25 * C;
• a processing aid such as a low viscosity silanol stopped siloxane fluid of a about 3 to 500 centipoise at 25 * C;
• a cross linking agent such as a polydimethyl siloxane polymethyl hydrogen siloxane random copolymer of about 100 repeating units each of PDMS and PMHS units.
• (H) a polydiorganosiloxane fluid of about 5,000 to 500,000 cps at 25 * C may be employed.
• the filler may be treated prior to compounding with up to 20 percent by weight based upon Component (C) of a cyclic methyl tetramer.
• the heat curable compositions of this invention have good clarity without sacrificing other beneficial physical properties such as tear strength, tensile strength, hardness, compression set elongation and oil resistance.
• Fig. 1 is a plot illustrating the effect of resin content ⁇ Component (B)) on clarity in a clear, heat curable silicone rubber composition of the present invention
• Fig. 2 is a plot illustrating the interaction of the filler treatment and the cross-linking agent on clarity and haze;
• Fig. 3 is a plot illustrating the interaction of the filler treatment and water on clarity and haze.
• Fig. 4 is a plot illustrating the interaction of the filler treatment and water on yellowing. DESCRIPTION OF THE INVENTION
• the present invention is directed to a heat curable silicone composition having excellent clarity, good tear and tensile strengths as well as desirable hardness, compression set, elongation and oil resistance.
• the composition contains a vinyl containing diorgano siloxane gum or gums having a viscosity of about 3,000,000 to 100,000,000 cps at
• the resin has a high Q content having sufficient compatibility with the other components so as to provide an essentially one phase system with the gum and filler.
• Compatibility is defined as a condition where the interface between the components, especially the gum and filler becomes substantially invisible.
• Component (A) is a vinyl containing diorgano siloxane gum or blend of such gums having a viscosity from about 3,000,000 to about 100,000,000 cps at 25 ' Z .
• the gum has a viscosity of between about 3,000,000 and 85,000,000 cps, more preferably, abou 20,000,000 to about 50,000,000 cps at 25 * C.
• the gum may have a weight percent vinyl concentration of from about 5xl0 ⁇ s to about 1.
• the gum preferably has a weight percent vinyl concentration in the range from about 6.5xl0" s to about 0.03, more preferably from about 8xl0' 5 to about 1.5x10"* and more preferably yet from about 8xl0" 5 to about 1.2xl0" 4 .
• the organo groups in the vinyl polymer or polymers of the gum should all be monovalent hydrocarbon radicals.
• the vinyl polymer or polymers of Component (A) may contain vinyl-on-chain groups and vinyl end-groups.
• the polymer is vinyl terminated. More preferably, the polymer is free of vinyl substitution except at the chain ends. In other preferred embodiments.
• Component (A) has the formula:
• Vi is vinyl;
• R 1 is independently chosen from monovalent hydrocarbon radicals, free of aliphatic unsaturation, and containing 1 to about 8 carbon atoms;
• R 2 is independently chosen from monovalent hydrocarbon radicals containing 1 to about 8 carbon atoms; and
• x and y are integers chosen such that Component (A) has a viscosity which ranges from about 3,000,000 to about 85,000,000 cps at 25 * C and a weight percent vinyl concentration in the range from about 5xl0" 5 to about 2x10"*, preferably from about 8xl0" 5 to about 1.5x10 " * and more preferably from about 8x10" 5 to about 1.2x10 " *.
• the vinyl containing polymers of Component (A) can be made by a process well known in the art, for example, by reacting cyclo-tetrasiloxanes in the presence of low molecular weight, linear vinyl chain stoppers at high temperatures in the presence of basic catalysts so as to yield a polymer of the desired molecular weight. When the reaction is over, the catalyst is neutralized and the excess cyclics are vented off to result in the desired polymer. By controlling the amount of chain stopper and the temperature of the reaction, the molecular weight of the desired vinyl-containing polymer end product can be controlled.
• a process well known in the art for example, by reacting cyclo-tetrasiloxanes in the presence of low molecular weight, linear vinyl chain stoppers at high temperatures in the presence of basic catalysts so as to yield a polymer of the desired molecular weight.
• the catalyst is neutralized and the excess cyclics are vented off to result in the desired polymer.
• the amount of gum present in the final product may vary. However, for purposes of explanation herein, it is assumed that 100 parts by weight of the gum is combined with varying amounts of the other components.
• the formulation has 80 parts of Component (A) . In each case, the amount of other components in the final product may be calculated or otherwise readily inferred.
• Component (A) is a vinyl-stopped polyorganosioxane gum about 9000 units in length.
• Component (B) is (1) an organopolysiloxane resin copolymer in an appropriate solvent (e.g. xylene) .
• the resin copolymer may contain R 3 SiO l 2 monofunctional units (M units) and Si0 2 quadrifunctional units (Q units) , where each R is independently selected from the group consisting of vinyl radicals and monovalent hydrocarbon radicals free of aliphatic unsaturation.
• M units monofunctional units
• Q units quadrifunctional units
• the ratio of M units to Q units ranges from about 0.5:1 to about 1.5:1, wherein the resin contains about 0.5 to 10.0 weight percent vinyl.
• Component (B) may comprise (2) an organopolysiloxane resin copolymer containing M and Q units as aforesaid and R 2 Si0 2/2 difunctional (D units) in an appropriate solvent where each R is independently selected from the group consisting of vinyl radicals and monovalent hydrocarbon radicals free of aliphatic unsaturation.
• Each M unit may represent M or M' e.g., M-vinyl units
• each D unit may represent D or D' e.g., D-vinyl units.
• the ratio of M units to Q units is from 0.5:1 to about 1.5:1 and the D units are present in an amount of from about 1 to 70 mol percent based upon the total number of mols of siloxy units in the copolymer.
• the resinous copolymer contains from about 0.5 to about 10.0 weight percent vinyl groups.
• the organopolysiloxane resin copolymer of Component (B) may contain mixtures of the MQ and the MDQ, resins
• organopolysiloxane resin copolymers of Component (B) in the present composition and their manufacture are well known in the art. Such resins are usually produced by hydrolysis of chlorosilanes in a process described in U.S. Patent No. 3,436,366 which is incorporated herein by reference.
• Component (B) is present in the composition of the present invention in an amount ranging from about 1.0 to about 30 and preferably from 1.0 to about 7.5 parts by weight based upon Component (A).
• the amount of resin present in the composition is most preferably governed by the amount of clarity desired in the final composition. It has been found that clarity increases greatly when the resin content is between l and 7.5 parts by weight relative to 100 parts by weight Component (A). This is best illustrated in Fig. 1 is a graph in which clarity is generally related to weight percent of Component (B) based on Component (A). It can be readily appreciated that the greatest increase in clarity occurs when Component (B) or resin content is between about 1 and about 7.5 parts by weight of Component (A). Thereafter, clarity increases marginally up to about 25 parts by weight whereupon additional resin concentrations apparently have little or no perceptible positive effect on the clarity.
• Component (B') in the examples below comprises (B2) dispersed in xylene. Much of the xylene has been vacuum stripped so as to result in a composition comprising 60% by weight solids and 40% by weight xylene.
• the process for manufacturing the composition includes a cook and strip step to facilitate the removal of the residual xylene from the finished compound.
• Component (C) comprises from about 5 to about 200, preferably from about 10 to about 100 and more preferably from about 20 to about 75 parts by weight of reinforcing fillers such as Si0 2 based on Component (A) .
• the filler is needed in the composition to provide a high tear strength.
• examples of reinforcing fillers that may be used include fumed silica and precipitated silica, with fumed silica being preferred.
• the filler may be treated with various agents so as to prevent the composition from structuring, for example cyclopolysiloxanes as disclosed in U.S. Patent No. 2,938,009 to Lucas and silazanes as disclosed in U.S. Patent No. 3,635,743 to Smith.
• the cyclopolysiloxanes present may be, for example, a cyclotetramethyl siloxane present in the amount of about 15 to 20 weight percent of the filler.
• Component (C) is fumed silica treated as in Lucas above having a surface area of about 160 mYgm to about 240 mVgrn. A further surface treatment with a linear vinyl containing silazane may be provided in-situ.
• Component (D) in the form of an organic peroxide free radical initiator or a curing catalyst is provided.
• the -11- preferred peroxide curing agents are thermal decomposition organic peroxides conveniently used to cure silicone elastomers. Examples of suitable organic peroxide free radical initiators for use in the present invention are disclosed, for example, in U.S. Patent No. 4,539,357 to Bobear which is incorporated herein by reference.
• Suitable peroxide catalysts include dial yl peroxide such as di-tertiary-butyl peroxide, tertiary- butyl-triethylmethyl peroxide, tertiary-butyl-tertiary- butyl-tertiary-triphenyl peroxide, t-butyl perbenzoate and a di-tertiary alkyl peroxide such as dicumyl peroxide.
• a platinum catalyst may be employed instead of an initiator.
• the preferred catalyst is a vinyl specific catalyst such as 2,5 dimethyl-2,5-di(t-butyl peroxy) hexane e.g., (Lupersol TM101).
• Component (E) a processing aid or plasticizer is employed.
• Component (E) is a low viscosity silanol stopped siloxane fluid having a viscosity ranging from about 3-500 cps and preferably 3 to 50 cps at 25 * C.
• the siloxane fluid is an equilibrium mix cf low molecular weight oligomers of from about 4 to about 10 but preferably between 4 and 6 repeating units m length with a minimum amount of cyclics in equilibrium with the oligomers.
• the processing aid (E) may have the form:
• the processing aid may be present in amounts up to 20 parts by weight based upon Component (A) , and preferably is present in amounts between 2 and 10 parts by weight based upon Component (A) and more preferably 3 parts by weight. It should be understood that, typically, the more filler that is used the greater amount of processing aid is employed.
• Component (F) may be vinyl stopped linear silazane such as divinyltetramethyl silazane.
• the material may be added for enhancing the bonding of filler to gum.
• the silazane acts as a filler treatment in-situ.
• Component (F) is preferably present in an amount up to 2 percent by weight, based upon the weight of Component (A) . More preferably, Component (F) is present in an amount of only up to about 0.3 parts by weight, based upon 100 parts by weight of Component (A) .
• Component (G) in the form of a hydride cross-linking agent may be employed.
• Component (G) may be a random copolymer formed of a polydimethylsiloxane (PDMS) and a polymethylhydrogensiloxane (PMHS) having the form:
• each R is independently chosen from a hydrogen or monovalent hydrocarbon radical free of aliphatic unsaturation containing 1 to about 8 carbon atoms, and x ranges from about 2 to about 100.
• the hydride is present in an amount of about 0.1 to 10 parts by weight based upon Component (A), preferably 0.5 to 8 parts by weight and more preferably 0.8 to 5 parts by weight based upon Component (A).
• a platinum catalyst may be substituted for the peroxide catalyst to cure the composition.
• Component (G) x may vary so that (G) has a viscosity ranging from about 5 to 500 cps, preferably from about 10 to about 100 cps and more preferably from about 10 to 50 cps at 25"C. In the examples below. Component (G) has a viscosity of about 30 centistokes, a hydride content of about 0.8 percent by weight, and a chain length of about 100 units.
• the linear hydride described above can be made by many procedures which are known in the art and particularly by the hydrolysis of appropriate chlorosilanes. See for example, U.S. Patent No. 4,041,101 which is incorporated herein by reference.
• Component (H) may be present in an amount of up to about 19 parts by weight based upon Component (A) .
• Component (H) is a vinyl-containing diorganopolysiloxane or a vinyl-containing diorganopolysiloxane blend having a viscosity of from about 5000 to about 500,000, preferably from about 40,000 to about 500,000, and most preferably from about 60,000 to about 150,000, centipoise at 25 * C.
• the vinyl polymer or polymers of Component (H) can be vinyl-terminated and can contain vinyl-on-chain units. In preferred embodiments, however, the vinyl polymer has no vinyl-on-chain units.
• the vinyl polymer of Component (H) has the formula:
• Vi is vinyl
• R l is selected from the class consisting of vinyl or alkyl radicals of 1 to about 3 carbon atoms
• R 2 is an alkyl radical of 1 to about 8 carbon atoms
• x and y vary such that the viscosity of (H) ranges from about 5,000 to about 500,000 centipoise at 25 * C, the vinyl concentration being in the range of from about 0.02 to about 0.1 weight percent.
• alkyl radicals which can be represented by R 1 and R 2 include methyl, ethyl, and vinyl radicals.
• R 1 is either vinyl or methyl
• R 2 is methyl.
• an organic peroxide free radical initiator or curing catalyst is provided.
• the preferred peroxide curing agents are thermal decomposition organic peroxides conveniently used to cure silicone elastomers. Examples of suitable organic peroxide free radical initiators for use in the present invention are disclosed, for example, in U.S. Patent No. 4,539,357 to Bobear which is incorporated herein by reference.
• Suitable peroxide catalysts include dialkyl peroxide such as di-tertiary-butyl peroxide, tertiary-butyl-triethylmethyl peroxide, tertiary-butyl-tertiary-butyl-tertiary-triphenyl peroxide, t-butyl perbenzoate and a di-tertiary alkyl peroxide such as dicumyl peroxide.
• a platinum catalyst may be employed instead of an initiator.
• the preferred catalyst is a vinyl specific catalyst such as 2,5 dimethyl-2,5-di(t-butyl peroxy) hexane e.g., (Lupersol TM 101) .
• the acid acceptor e.g., MgO soaks up acid liberated during curing. This acid would otherwise cause cleavage of the product chains.
• Copending U.S. patent application Serial No. 07/587,876, filed 9/25/90, attorney docket no. 60SI- 1336, incorporated herein by reference discloses heat curable silicone rubber compositions containing blends of vinyl containing organopolysiloxane gums and oils, MQ and MDQ resins, filler and a process aid are cured with a peroxide initiator.
• the compositions are formulated for increased tear strength and reduced compression set properties. While optical properties such as increased clarity and reduced haze are not properties which are discussed in Ward et al. Nevertheless, modified versions of one or more compositions disclosed therein are useful materials for use in a clear, heat curable silicone rubber of the present invention.
• Components (A), (C) and (E) (sometimes hereafter referred to as common components) were compounded with varying amounts of Components (D), (F), (G) and (H) .
• the common components include: 80 parts by weight of Component (A) comprising a vinyl chainstopped polydimethylsiloxane gum having about 4,000 to about 10,000 repeating units so as to result in a viscosity of about 13 million cps at 25'C;
• Component (C) comprising a finely divided silica filler having a surface area of about 240m 2 /gm; and and 4 parts of Component (E) comprising a silanol stopped fluid having a viscosity between 3 and 30 cps at 25'C.
• Component (H) comprising a vinyl chain-stopped polydimethylsiloxane high viscosity oil having about 1,000 repeating units and a viscosity of about 60,000 cps at 25 C;
• Component (G) comprising a polydimethylsiloxane polymethylhydrogensiloxane hydride random copolymer with about 100 repeating units;
• composition (F) comprising a divinyl tetramethyl silazane
• Tables 1A-1C list the resulting compositions and their corresponding properties.
• Test data were obtained from the following ASTM methods and procedures: Shore A - D-2240; Tensile, Elongation and modulus - D-412 (Die C) ; Tear - D-624 (Die B) ; and Compression Set - D-395 (method B) .
• Table II represents a tabulation of results observed when various properties were evaluated for EXAMPLES 1-19.
• the upper half of the table lists the five modifiers and their particular effect on the various properties.
• a plus sign (+) indicates that the particular modifier has a positive or increasing effect on the numerical value of the measured property and a minus sign (-) indicates that the modifier decreases the numerical value of the measured property.
• S indicates significant effects are measured; and a blank indicates no significant effects are measured.
• Component (B') has a positive effect on transmission or clarity increasing the % transmission and decreasing both the haze and yellow index.
• Component (H) is normally used as a resin carrier and has no significant effect on the clarity but may suppress tear B, Shore A, and tensile strength.
• the hydride cross linking agent, Component (G) decreases yellowness and has a positive effect on strength.
• increasing amounts of linear vinyl silazane (F) decreases haze and yellowness, has a negative effect on elongation and has a positive effect on tear B, Shore and tensile strength. The water does not seem to have any significant effect on the properties directly.
• Table II illustrates the interactions between the components. It can be seen that the hydride, Component (G) and the water have significant interacting effects on haze, yellowness and tear B. Likewise the hydride and linear vinyl silazane (F) have a significant effect on haze.
• the resin (B') interacts with the hydride (G) to effect tear B and the resin (B') interacts with both the oil (G) and the linear vinyl silazane (F) to effect tensile strength.
• Fig. 2 illustrates the interaction between the silazane (F) and the hydride (G) . The plot illustrates that increasing amounts of the silazane decreases the haze and yellowness the most when the hydride is reduced.
• Fig. 3 shows that haze is reduced and therefore clarity increases when the water content is high with a corresponding reduced hydride (G) content or with a reduced water content and increasing hydride content.
• Fig. 4 graphically illustrates that yellowness is decreased with increasing hydride content. However, increasing the water content suppresses the advantageous reduction in yellowness.
• Tables III-(A), (B) and (C) numerically illustrate the effects graphically illustrated in Figs. 2-4.
• haze is reduced when the silazane content is High and the hydride content is Low, which is desirable in accordance with the present invention.
• water content is reduced in comparison to the hydride, haze is reduced (clarity is improved) .
• yellowness is reduced as the hydride content increases with decreasing water content, as illustrated on Table III-(C) .

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